If $20$ pumps working a fixed number of hours per day can drain a flooded area in $7$ days, how many days…

If $20$ pumps working a fixed number of hours per day can drain a flooded area in $7$ days, how many days will $14$ pumps (working the same hours per day) take?
  1. $8$
  2. $9$
  3. $10$
  4. $12$

Solution

$20 \times 7 = 14 \times d \Rightarrow d = \dfrac{140}{14} = 10$ days.

Asked in: IMO

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